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排序方式: 共有657条查询结果,搜索用时 312 毫秒
651.
Dinesh Varshney A. Yogi K.K. Choudhary 《Physica C: Superconductivity and its Applications》2010,470(22):2016-2022
In this paper, we undertake a quantitative analysis of observed temperature-dependent in-plane normal state electrical resistivity of single crystal YBa2Cu4O8. The analysis is within the framework of classical electron–phonon i.e., Bloch-Gruneisen model of resistivity. It is based on the inherent acoustic (low frequency) phonons (ωac) as well as high frequency optical phonons (ωop), the contributions to the phonon resistivity were first estimated. The optical phonons of the oxygen breathing mode yields a relatively larger contribution to the resistivity compared to the contribution of acoustic phonons. Estimated contribution to in-plane electrical resistivity by considering both phonons i.e., ωac and ωop, along with the zero-limited resistivity, when subtracted from single crystal data infers a quadratic temperature dependence over most of the temperature range [80 ? T ? 300]. Quadratic temperature dependence of ρdiff. = [ρexp − {ρ0 + ρe−ph (=ρac + ρop)}] is understood in terms of electron–electron inelastic scattering. The relevant energy gap expressions within the Nambu-Eliashberg approach are solved imposing experimental constraints on their solution (critical temperature Tc). It is found that the indirect-exchange formalism provides a unique set of electronic parameters [electron–phonon (λph), electron-charge fluctuations (λpl), electron–electron (μ) and Coulomb screening parameter (μ*)] which, in particular, reproduce the reported value of Tc. 相似文献
652.
MgB2 polycrystalline superconducting specimens were irradiated with several doses of γ‐rays up to 100 MR. An increase in the normal state resistivity and a broadening of the resistive transition to the superconducting state were observed with increasing γ‐irradiation dose. Although very small changes to the superconducting transition temperature were obtained after γ‐irradiation, different temperature dependence of normal‐state resistivity and different residual resistivity ratios, RRR were obtained for different doses. We have found a correlation between RRR and the power law dependence of resistivity, n as the irradiation dose increases. This correlation may be an indication that the electron‐phonon interaction is important in these samples. These results are attributed to the disorder caused by γ‐rays. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
653.
The electrical resistivity of Ag was experimentally measured at high pressures up to 5?GPa and at temperatures up to ~300?K above melting. The resistivity decreased as a function of pressure and increased as a function of temperature as expected and is in very good agreement with 1 atm data. Observed melting temperatures at high pressures also agree well with previous experimental and theoretical studies. The main finding of this study is that resistivity of Ag decreases along the pressure- and temperature-dependent melting boundary, in conflict with prediction of resistivity invariance. This result is discussed in terms of the dominant contribution of the increasing energy separation between the Fermi level and 4d-band as a function of pressure. Calculated from the resistivity using the Wiedemann–Franz law, the electronic thermal conductivity increased as a function of pressure and decreased as a function of temperature as expected. The decrease in the high pressure thermal conductivity in the liquid phase as a function of temperature contrasts with the behavior of the 1 atm data. 相似文献
654.
Jose Fidel Chavez Juan Jorge Martinez-Vega Noureddine Zouzou Jean Guastavino 《Macromolecular Symposia》2004,212(1):485-490
Polymers find an important field of application in the electrical industry because of their utilization as insulators and dielectrics. The challenge over the last several years has been to make electrical compounds smaller in size. In that way the material morphology is of strategic importance in the performance of new components in relation to their geometry. Therefore, it is important to know the influence of different types of stress on electric properties of the materials. We have studied the influence of the crystallinity on electric conductance of poly(ethylenenaphthalene-2,6-dicarboxylate) (PEN), which is increasingly replacing some dielectrics (polypropylene and PET) in certain electric applications. Starting from an amorphous PEN, samples with various crystallinities were obtained and analyzed using DSC in order to determine their thermal characteristics. Moreover, measurements of charge and discharge currents were carried out on PEN samples to characterize their electric properties. The steady state current observed after 120 min, in response to the electric field, shows an increase in the insulator resistivity with the crystallinity. The increase in the crystallinity favors a decrease in the free volume, so the movement of charges is restricted especially by the species of large sizes. 相似文献
655.
E. Hernndez L. Durn C. A. Durante Rincn G. Aranguren C. Guerrero J. Naranjo 《Crystal Research and Technology》2002,37(11):1227-1233
From electrical resistivity measurements in the range from 240 to 450 K and from optical absorption measurements the energy gap value of CuIn5Se8 has been found to be 1.13 eV. Thermally stimulated current and electrical measurements at high temperature performed in indium annealed samples show deep levels at 0.55 and 0.79 eV, respectively. These defects are expected to be associated with interstitial indium or indium in copper site because of the In‐rich condition. 相似文献
656.
Systematic dark electrical resistivity and Hall mobility measurements have been carried out in the temperature range 150‐400 K on n‐type GaS0.5Se0.5 layered crystals. The analysis of temperature dependent electrical resistivity and carrier concentration reveals the extrinsic type of conduction with a donor impurity level located at 0.44 eV, donor and acceptor concentrations of 3.4 ×1017 and 4.1×1016 cm‐3, respectively, and an electron effective mass of 0.41 m0. The Hall mobility is limited by the electron‐phonon short‐range interactions scattering at high temperatures combined with the ionized impurity scattering at low temperatures. The electron‐phonon short‐range interactions scattering mobility analysis reveals an electron‐phonon coupling constant of 0.25 and conduction band deformation potential of 5.57 eV/Å. 相似文献
657.
《印度化学会志》2023,100(5):101006
Electrodeposition approach was used to grow the ZnSe nanostructure on indium doped tin oxide (ITO) layered glass substrate. Due to low cost and high degree of absorption, binary semiconductors made from chalcogens such as CdSe, ZnO, ZnS and ZnSe provide significant features in photovoltaic and photoelectrochemical cells. The structural and morphological properties of deposited nanostructures were examined by XRD and SEM. X-ray diffraction analysis informed about cubic structure with a preferred orientation and the calculated crystal size was approximately 75 nm. The optical properties were examined by UV–visible absorbance spectra and optical band gap was measured using Tauc plot. The deposited ZnSe nanostructure has direct band gap ∼2.52 eV at room temperature which was less than 2.82 eV which is the band gap of bulk ZnSe. Investigations also focused on additional qualities like excellent optical transmission, low electrical resistance, and good photosensitivity. Because of the presence of defect states in the deposited nanostructure, the band gap energy is smaller than that of bulk material. The current-voltage characteristics were measured in dark mode and under illumination of normal tungsten filament light and LED. There was notable change in the current for both normal light and LED in comparison to dark mode. The findings of all the characterization methodologies suggested that for the production of solar cells low cost ZnSe may be used as an alternative environment friendly Cd-free window layer. 相似文献